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// Copyright 2019 The Hugo Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package tableofcontents
import (
"strings"
)
// Headers holds the top level (h1) headers.
type Headers []Header
// Header holds the data about a header and its children.
type Header struct {
ID string
Text string
Headers Headers
}
// IsZero is true when no ID or Text is set.
func (h Header) IsZero() bool {
return h.ID == "" && h.Text == ""
}
// Root implements AddAt, which can be used to build the
// data structure for the ToC.
type Root struct {
Headers Headers
}
// AddAt adds the header into the given location.
func (toc *Root) AddAt(h Header, row, level int) {
for i := len(toc.Headers); i <= row; i++ {
toc.Headers = append(toc.Headers, Header{})
}
if level == 0 {
toc.Headers[row] = h
return
}
header := &toc.Headers[row]
for i := 1; i < level; i++ {
if len(header.Headers) == 0 {
header.Headers = append(header.Headers, Header{})
}
header = &header.Headers[len(header.Headers)-1]
}
header.Headers = append(header.Headers, h)
}
// ToHTML renders the ToC as HTML.
func (toc Root) ToHTML(startLevel, stopLevel int, ordered bool) string {
b := &tocBuilder{
s: strings.Builder{},
h: toc.Headers,
startLevel: startLevel,
stopLevel: stopLevel,
ordered: ordered,
}
b.Build()
return b.s.String()
}
type tocBuilder struct {
s strings.Builder
h Headers
startLevel int
stopLevel int
ordered bool
}
func (b *tocBuilder) Build() {
b.writeNav(b.h)
}
func (b *tocBuilder) writeNav(h Headers) {
b.s.WriteString("<nav id=\"TableOfContents\">")
b.writeHeaders(1, 0, b.h)
b.s.WriteString("</nav>")
}
func (b *tocBuilder) writeHeaders(level, indent int, h Headers) {
if level < b.startLevel {
for _, h := range h {
b.writeHeaders(level+1, indent, h.Headers)
}
return
}
if b.stopLevel != -1 && level > b.stopLevel {
return
}
hasChildren := len(h) > 0
if hasChildren {
b.s.WriteString("\n")
b.indent(indent + 1)
if b.ordered {
b.s.WriteString("<ol>\n")
} else {
b.s.WriteString("<ul>\n")
}
}
for _, h := range h {
b.writeHeader(level+1, indent+2, h)
}
if hasChildren {
b.indent(indent + 1)
if b.ordered {
b.s.WriteString("</ol>")
} else {
b.s.WriteString("</ul>")
}
b.s.WriteString("\n")
b.indent(indent)
}
}
func (b *tocBuilder) writeHeader(level, indent int, h Header) {
b.indent(indent)
b.s.WriteString("<li>")
if !h.IsZero() {
b.s.WriteString("<a href=\"#" + h.ID + "\">" + h.Text + "</a>")
}
b.writeHeaders(level, indent, h.Headers)
b.s.WriteString("</li>\n")
}
func (b *tocBuilder) indent(n int) {
for i := 0; i < n; i++ {
b.s.WriteString(" ")
}
}
// DefaultConfig is the default ToC configuration.
var DefaultConfig = Config{
StartLevel: 2,
EndLevel: 3,
Ordered: false,
}
type Config struct {
// Heading start level to include in the table of contents, starting
// at h1 (inclusive).
StartLevel int
// Heading end level, inclusive, to include in the table of contents.
// Default is 3, a value of -1 will include everything.
EndLevel int
// Whether to produce a ordered list or not.
Ordered bool
}
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